1. Field of the Invention
The present invention relates to a stereoscopic image capture device, and specifically relates to a technique of forming object images passing through different regions of an imaging optical system on respective imaging elements and acquiring a stereoscopic image formed with a plurality of parallax images.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 2009-168995 (hereinafter referred to as PTL 1) discloses a ranging device that calculates a defocus amount by arranging two polarization elements with mutually orthogonal polarizing axes in the pupil position of a monocular optical system, separating light fluxes passing through these polarization elements by a beam splitter, entering them into two imaging elements, taking two images and comparing the phase difference of an object in two images in the same way as phase difference AF.
Also, PTL 1 contains description that stereoscopic image capture is possible by taking two images, especially, contains description that it is possible to adjust the stereoscopic effect of a stereoscopic image taken in a monocular optical system by changing the F value of a pupil mask (paragraph [0047] of PTL 1).
Further, PTL 1 describes three kinds of pupil masks selected by the F value of the optical system, where each pupil mask has a pair of openings with mutually different distances from the light axis of the optical system. Subsequently, in a case where the F value is small (bright), the ranging accuracy is maintained by using a pupil mask having the most remote pupil region from the light axis, and, since a light flux from the periphery is restricted as the F value becomes large (dark), a pupil mask with a pair of openings close to the light axis of the optical system is selected. Moreover, these pupil masks are selected according to the open F value, and, in a case where the F value varies by focal length, appropriate focus detection is always enabled by switching it according to the focal distance.
Japanese Patent Application Laid-Open No. 2008-242182 (hereinafter referred to as PTL 2) describes a focus point detection device that performs focus point detection in a pupil-division-type phase difference detection system. In this focus detection device, the maximum image surface defocus amount of an interchangeable lens is substantially proportional to the focal length. Therefore, in a case where the focal length is equal to or greater than a predetermined value, the diaphragm is set to the F value darker than the open F value to perform focus point detection, and, in the following case, the diaphragm is set to the F value darker than the open F value to prohibit execution of the focus point detection or the diaphragm is set to the F value darker than the open F value to adjust the F value in the case of performing the focus point detection according to the focal length (paragraph [0053] of PTL 2).